VOICE OVER WiFi

by

Narendranath KanukolanuRahul DattaKalyan Valluri

TOPICS 1. Introduction What is WiFi What is voice over WiFi What is voice over IP 2.Features 3.Architecture of Voice over WiFi 4.Future prospects 5. Conclusion

WHAT IS WiFi(wireless fidelity)

WiFi is the wireless way to handle networking. It is also known as 802.11 networking and

wireless networking. The big advantage of WiFi is its Simplicity. Can connect computers anywhere in home or

office without the need for wires. The computers connect to the network using

radio signals.

Contd…

Wireless Fidelity is meant to be used generically when referring of any type of 802.11 network, whether 802.11,802.11a, 802.11b, 802.11g dual-band, etc. The term is promulgated by the Wi-Fi Alliance.

WiFi Alliance An organization made up of leading wireless equipment and software providers.

Over view of IEEE 802.11? Wireless networking hardware requires the use

of underlying technology that deals with radio frequencies as well as data transmission.

The most widely used standard is 802.11 produced by the Institute of Electrical and Electronic Engineers (IEEE). This is a standard defining all aspects of Radio Frequency Wireless Networking.

Specifications in the 802.11 family

802.11 Applies to wireless LANs and provides 1 or 2 Mbps transmission

in the 2.4 GHz band using either Frequency Hopping Spread Spectrum (FHSS) or Direct Sequence Spread Spectrum (DSSS).

802.11a An extension to 802.11 that applies to Wireless LANs and

provides up to 54 Mbps in the 5GHz band. 802.11a uses an Orthogonal Frequency Division Multiplexing encoding scheme rather than FHSS or DSSS. H

Contd..

802.11b (also referred to as 802.11 High Rate or Wi-Fi) An extension to 802.11 that applies to wireless LANS and

provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1 Mbps) in the 2.4 GHz band.

802.11g Applies to wireless LANs and provides 20+ Mbps in the 2.4 GHz

band.

IEEE 802.11 WLAN Standards

An 802.11 WLAN History

1940: Spread spectrum technology first used by the military 1980: Limited applications using narrowband technology 1989: FCC assigns frequency for commercial use. ISM bands authorized (900 MHz, 2.4 GHz, 5 GHz) 1990: *900 MHz products begin shipping *IEEE begins work on industry standard 1994: 2.4 GHz products begin shipping 1997: *IEEE 802.11 standard approved. *2.4 GHz products begin dominating the scene 1999: *IEEE 802.11a&b supplements ratified.

*WECA formed for interoperability testing *Wide Band Frequency Hopping NPRM Released by FCC “Enhanced MAC - QoS and Security” Task Group chartered

2001 QoS/Security draft standard formulated 2002 Has over 130 participating companies with voting

members

Technology that makes WiFi networking possible

The Walkie Talkie Network These are small radios that can transmit and

receive radio signals. When you talk into a Walkie-Talkie, your voice is picked up by a microphone, encoded onto a Radio frequency and transmitted with the antenna. Another walkie-talkie can receive the transmission with its antenna, decode your voice from the radio signal and drive a speaker.

WiFi's Radio Technology WiFi radios that work with the 802.11b and

802.11g standards transmit at 2.4 GHz. while those that comply with the 802.11a

standard transmit at 5 GHz. WiFi radios use efficient coding techniques that

also contribute to the much higher data rates. For 802.11a and 802.11g, the technique is

known as Orthogonal Frequency-Division Multiplexing (OFDM). For 802.11b, it is called Complementary Code Keying (CCK).

Wifi SECURITY WiFi hotspots can be open or secure. If a

hotspot is open, then anyone with a WiFi card can access the hotspot. If it is secure, then the user needs to know a WEP key to connect.

WEP stands for Wired Equivalent Privacy.

Hardware needed to create WiFi Network

One of the best things about WiFi is how simple it is. 802.11a, 802.11b or 802.11g network card. 802.11g has the

advantage of higher speeds and good interoperability on 802.11b equipment. For a laptop, this card will normally be a PCMCIA card that you

slide into a PCMCIA slot on your laptop. Or you can buy a small external adapter and plug it into a USB port.

For a desktop machine, you can buy a PCI card that you install inside the machine, or a small external adapter that you connect to the computer with a USB cable.

Install the card Install the drivers for the card Find an 802.11 hotspot Access the hotspot. (A hotspot is a connection point for a

WiFi network)

Requirements

VoIP(Voice over Internet Protocol)

A category of hardware and software that enables people to use the Internet as the transmission medium for telephone calls by sending voice data in packets using IP rather than by traditional circuit transmissions of the PSTN (Public Switched Telephone Network).

In short VoIP  transfers voice through IP packets over the Internet.

Contd..

Internet telephony products are sometimes called IP telephony, Voice over the Internet (VOI) or Voice over IP (VoIP) products.

The voice traffic is converted into Data packets then routed over the Internet, or any IP network as normal data packets would be transmitted. When the data packets reach their destination, they are converted back to voice data again for the recipient.

How does VoIP work? A number of years ago sending a signal to a

remote destination could be done digitally. VoIP works by digitalizing voice in data packets, sending and reconverting them in voice.

Advantages of Digital Formats

Digital format can be better controlled. Compressed. Routed and converted to a new better format. Noise is tolerant than analog signals. VoIP uses TCP/IP (TCP/IP is an Internet protocol

with a leading IP packet to control communication and the payload).

Home phone and one computer

Home Phone with more than one computer

Advantages of VoIP It makes long-distance calls less expensive by

removing some of the access charges required for use of the public telephone network.

A user's physical location also becomes irrelevant.

VoIP also enables WiFi’s advanced features like checking voice mail or programming call forwarding through a web application.

Disadvantages of VoIP VoIP services do not work in blackouts. VoIP services are only as reliable as the

customer’s broadband connection.  A poor quality connection can lead to voice

quality issues. Luckily, high quality broadband is getting easier and easier to find these days.

VoWiFi(Voice over Wireless Fidelity )

Simply means a Wi-Fi based VoIP Service or in even more general terms, a wireless based VoIP system.

Where VoIP consists of the hardware and software that enables people to use the Internet as the transmission medium for telephone calls.

VoWiFi is the wireless version of  this technology that is designed to work on wireless devices such as a laptop or PDA.

Contd.. Mobile voice over IP (VoIP) is currently limited

to voice over WiFi (VoWiFi) but, with the introduction of cellular technologies providing higher bandwidth capabilities, VoIP is likely to move towards cellular networks.

Over view of VoWiFi VoWiFi is a term used for technologies or

services which provide voice over WiFi WiFi refers to any wireless LAN products or

services that are based on the IEEE 802.11 WLAN standard with theoretical data rates ranging from 11M to 54 Mbit/sec.

A hotspot is a wireless LAN node that provides Internet connection and virtual private network (VPN) access from a given location

Contd.. With combined VoWiFi/cellular phone and

seamless roaming between those two networks, subscribers could use voice over a WiFi network, where available, and cellular connections where WiFi is missing or outside of a WiFi area.

Combining VoIP with WiFi has a great potential to reduce the cost of voice services, in particular for roaming and for access to broadband services, while increasing the convenience to users.

Deployment of VoWiFi The requirements of the three main

segments making up the WLAN marketplace also will have an effect on the deployment parameters of WLANs. These three market segments are

Contd.. Residential/SOHO (small office, home office)

cordless phones or scaled down PBXs that will function as part of an integrated gateway

Enterprise mobile VoIP WLAN network (private network)

Cellular off-load network (VoIP over WLAN in hot spots, which in turn interfaces to the public telephone network)

Such a network would allow seamless multiple access options for most of the more prevalent voice and data services.

Architecture Requirements In the context of Vo WiFi and VoWiFi-Mobile

roaming many of the current deployments of VoWiFi involve integration with enterprise PBXs

One method of integrating with a traditional PBX is to use a Vo WiFi gateway.The calls are routed from the Vo WiFi phone to Vo WiFi gateway via the WiFi Access Point and the Vo WiFi gateway transmits calls to the existing PBX.Integration with PBX allows calls to be placed to and received from the PSTN, and also supports PBX features such as call forwarding messaging and conference calling.

Contd.. Another way to use Vo WiFi is to use

softphones on mobile computers or PDAs which route calls entirely over the internet in WiFi areas such as HOT SPOTS.

Architecture Of VoWiFi

Contd.. The gateway connects to the mobile switching centre for

cellular calls, and connects to the data network for WiFi calls.

The gateway manages subscriber access and handoff. As the subscriber moves within range of a wireless access point, the gateway authorizes the subscriber’s access and all network services — both voice and data — are delivered over the WiFi.

When the subscriber moves outside of the WiFi coverage area, the gateway seamlessly switches control over to another WiFi network or the mobile networkdeploying a VoWiFi/mobile roaming solution requires dual-mode handsets that support both VoWiFi as well as mobile

Drivers of VoWiFi Development and VoWiFi/mobile Convergence WiFi and VoIP are being widely deployed in

enterprises. WiFi is easy and flexible to deploy, and is

claimed to be more reliable in terms of coverage while costing less than traditional cellular services.

It is also expected that using VoWiFi new converged applications can be developed for mobile workers with new capabilities such as geographic location information and instant messaging.

Contd.. In this early stage of the VoWiFi market, the

handsets and VoWiFi services have been focused on enterprise or corporate users and are expected to do so in the next few years

The main reason is because VoWiFi is related to the increasing deployment of WiFi and VoIP in corporate environments

Why would mobile service providers want to provide VoWiFi? At first glance, it would seem that mobile

operators would be disadvantaged by providing roaming services with WiFi because they may lose revenue generated by traditional mobile roaming services.

Generally, WiFi services are provided at a lower price than mobile services or even free, which has induced mobile service providers, especially 3G service providers, to consider WiFi and VoWiFi services to be competitive with their mobile services.

Contd.. recent proliferation of WiFi in enterprises and in

the number of hotspots in densely populated areas in a relatively short period of time, several mobile service providers have started to regard VoWiFi and VoWiFi/mobile roaming as a way of reducing prices for their customers and consider WiFi as a means to enhance competition and differentiate their service from that of competitors.

Impact of WiFi and VoWiFi on 3G Development

VoWiFi, or VoIP over WiFi, allows users to make voice calls and access video and data at a low price.

The development of this service will have an impact on 3G services and the way they are structured and priced

While 3G has the advantage of ubiquitous access, the data transfer speed is about a half megabit per second slower than WiFi’s top speed.

User benefits from VoWiFi interconnecting with mobile networks Users of dual handsets will be able to make

calls more cheaply than those using mobile phones.

Calls generated in hotspots or WLANs are likely to result in considerable savings by consumers.

VoWiFi also provides innovative new features such as the ability to access e-mail, Internet, location information, etc. at a lower price

Contd.. Another benefit for existing users of

VoWiFi service is that they are no longer constrained in obtaining service from a limited area such as a hotspot or within a company, but are able to have real mobility and ubiquitous access to voice calls as well as data and video by seamless interconnection with mobile networks with a single handset or portable computer

IEEE 802.11 Protocol Architecture

Technical issues and standard development of VoWiFi

Since VoWiFi is technically based on VoIP over WiFi, quite a few technical issues and challenges are similar to those in WiFi and VoIP

Quality of Service (QoS) WiFi has its own QoS challenges in that throughput

may fluctuate when roaming among Access Points. Subscribers are more sensitive to perceptible

service degradation for voice or video than for data. Therefore, more reliable QoS is necessary for voice to be delivered satisfactorily over WiFi

Contd.. The issue of QoS will be increasingly important when roaming

between WiFi and mobile networks is supported, given that network hand-off can result in quality of service degradation.

Up to now, most wireless equipments did not yet incorporate QoS because they were to emerge. Without standards, local voice systems over WiFi have been provided as bundles of proprietary wireless network hardware and software.

The WiFi Alliance announced a new WiFi Multimedia (WMM) program to deal with quality of service issues in September 2004.41 The WMM program combines core elements of the 802.11e draft and a simplified packet priority access category scheme borrowed from IEEE 802.11d. WMM is designed to improve the QoS for voice, audio, video and multi-media applications over WiFi.

Quality of Service is hard to find these days, but QoS standards for high quality VoWiFi are a work in progress. 802.11e

802.11e includes what the Wi-Fi Alliance phrases as Wi-Fi Multimedia Extensions (WMM, or WME) for prioritization.

Contd..

Contd.. WMM includes four access categories: Voice Priority, the highest level, is intended

to support multiple simultaneous, toll-quality voice calls with low latency.

Video Priority, the next highest level, prioritizes video relative to all other data traffic. One 802.11a/g channel can support three-four SDTV (Standard Definition TV) data streams, or one HDTV (High Definition TV) stream.

Contd.. Best Effort Priority is intended to support

traffic from legacy devices, or from applications or devices that lack QoS capabilities. Best effort traffic is less sensitive to latency than voice or video. Internet surfing is an example.

Background Priority is intended to support low priority traffic that does not have strict latency and throughput requirements. File downloads and print jobs are cited as examples.

Contd.. There exist a number of proprietary QoS

mechanisms such as SpectraLink Voice Priority (SVP), used on SpectraLink phones.

QoS requires not only prioritization, but also smooth handoffs as the handset moves from cell to cell.

Proper bandwidth With the wide deployment of WiFi in hotspots and in

enterprises, the need for higher-speed WiFi is also increasing. Applications over WiFi use an increasing amount of bandwidth The number of users and devices connecting to WiFi are

increasing and the bandwidth demand is expected to increase with the provision of WiFi/mobile roaming

Security and privacy The potential security and privacy risks arising from using WiFi

for voice have been an obstacle to further development of VoWiFi/mobile roaming

Those risks include stealing packets, unauthorised access to the network and intentional interference by outsiders whichhas a greater impact on business users than residential subscribers.

In general, encryption presently used such as Wired Equivalent Privacy (WEP) is considered weak and susceptible to outside intrusion

Interoperability The adoption of heterogeneous WiFi technologies may cause

incompatibilities With the advance of WiFi and VoWiFi, a growing number of

vendors are trying to differentiate their products beyond existing standards, mainly by boosting speed or security.

Interference and complexity The spectrum for WiFi is not dedicated and licensed for use by

certain entities as in the case of mobile services. Therefore, the users of WiFi share spectrum with other devices, including

household devices such as microwaves. Consequently, as WiFi or VoWiFi deploys further, the spectrum

will become increasingly crowded and the possibility of interferences will grow

Various facts of network capacity planning

for the future deployment of VoWLAN Over-subscription of voice networks (voice

concentration) Throughput requirements for typical voice,

video and media applications using IP packet technology

WLAN network capacity for enterprise applications RF frequency planning and reuse for large network deployments WLAN network capacity for home applications

Consideration of wireless repeaters (mesh) to extend home coverage

Over-subscription of Voice Services (Concentration)

A basic understanding of oversubscription, for example, can assist network planners who are evaluating network capacity for enterprise VoIP over WLAN applications.

PSTN Phone lines typically are terminated at a Class 5 switch or a Digital Loop Carrier (DLC) connected to a Class 5 switch. The Class 5 switch manages call connections and rejects calls when the system capacity has been reached

Contd.. In cellular networks, some consideration is

given to reserve a fraction of the active phone line capacity for handoff purposes between one cell and the next.

Voice Throughput over IP Voice Compression and VoIP Voice compression algorithms help US

TO derive as much capacity from an infrastructure as possible, but compression algorithms involve tradeoffs between efficiency and overhead that planners should consider.

In wireless networks, voice is digitized with the G.711 coding standard and transported at 64 Kbps.

Contd.. While G.711 is the mainstream digital codec for

tollquality voice services, a number of more efficient codes are used for both cellular and voice "pair gain applications."

In an IP network, voice codecs are placed into packets with durations of 5, 10 or 20 msec of sampled voice, and these samples are encapsulated in a VoIP packet.

Throughput of WLAN Access Points

To optimize the network capacity of a WLAN with a voice special attention to the throughput of the APs which govern how quickly data of any sort can be placed on the network has to be given.

Contd.. The following two basic functions affect the

throughput of an AP: 1. Area and modulation density supported

by the cell a. Small cells can support high data

rate modulations (peak rates) b. Larger cells will use lower rate 802.11

modulations and are an aggregate sum of areas covered and

the modulation rate

Contd.. 2.The WLAN MAC protocols have the following effects: a. The Ethernet (CSMA/CA) protocols, DCF and EDCF, limit

capacity at approximately 37% of the peak data rate

b. Scheduled TDMA protocols such as HCF can theoretically reach

around 90% capacity of the network, but under full load they will

typically carry only approximately 75% of capacity c. DCF/EDCF MAC protocols do not effectively manage

network latencies as the capacity limit is approached

d. HCF protocols control latencies by providing fair weighted

queuing so that all users will receive service even under full load

conditions

Application of Small-mesh Access Points for Residential Coverage

Access points for the residential/SOHO marketplace, cell coverage and throughput are the most crucial issues facing WLAN implementations in this market.

Wireless repeaters, which can be used to implement small mesh residential networks, are a low-cost method of improving coverage and throughput.

Contd.. One possible technique for extending coverage

and improving residential service is the use of multiple APs in a mesh/repeater architecture.

Residential Network Topology

A simple example featuring two access points

Contd.. There are two possibilities for operating a

residential mesh network. They are the following:

Single-Frequency Mode: Access points are not dual-mode and can only support a single frequency of operation from an AP to another AP and from an AP to a client/subscriber.

Dual-Frequency Mode: Access points are dual frequency, supporting two separate links on two separate frequencies simultaneously.

Dual Frequency Mode

Access Time Delay The time delay and jitter of the VoIP system will

be a design consideration. The two following issues relate to time delay and jitter: 1. Signaling for call set up, tear down and other call

control communications will be delayed. (Worst case delay is the principal concern.)

2. Jitter in the voice traffic/bearer channel will cause delay.

Delays in the communication path for an enterprise network

Delays in the communication path for an Residential network

Deploying VoIP over WLANs The technology needed to deploy VoIP over

WLANs and the other wireless applications is being incorporated into next generation handsets, mobile devices, personal digital assistants (PDAs), laptop computers, infrastructure systems and other types of systems.

Dartmouth Deployment Full VOIP Software by end of 2003 Campus wide WLAN Network 1000 Freshman Outbound, Inbound Calls Free Wired, Wireless & LD PCs, PDAs, other devices Traffic & Usage Study 13,000 Students, Faculty & Staff

Advantages of VoWiFi Mobility is the primary selling point, much as it

is with cell phones. VoWiFi has the advantage of no airtime

charges. As a wireless technology, there are no wires to run to Wi-Fi phones. Therefore, network configuration and reconfiguration processes are fast.

Disadvantages of VoWiFi VoIP and Wi-Fi are both immature technologies,

so merging the two into VoWiFi carries some associated risks.

Standards are still in development, and some early pre-standard versions may not be upgradeable to compliance level.

As a data-centric LAN technology, Wi-Fi involves a shared medium in the form of frequency bands creating issues of contention and congestion.

Contd..

Troublesome for stream-oriented communications such as voice, and especially so when handoffs are required as the user roams between APs.

Costs have to be considered, of course, and the cost of a VoWiFi LAN can be double that of a data-only WLAN.

Wi-Fi phones are easily double the cost of a typical cordless phone.

Contd.. Current Wi-Fi phones don’t have much,

although the next generation or two should overcome that issue.

Benefits VoWiFi delivers a simpler, less expensive and

more flexible system for providing mobile data and voice communications than other technologies that require the implementation and maintenance of separate systems for each.

VoWiFi also offers greater reliability and voice quality than alternatives such as cellular technology.

Technical Challenges

Deliver High Quality without QoS Deal with High Packet Loss on WLANs Roaming Across WLAN Network

Segments Roaming From WLAN to Cellular Compatibility with Firewalls

FUTURE The number of businesses using voice over

wireless local area networks (VoWLAN) is set to triple over the next two years

A new report from Infonetics Research has found that 10 per cent of north American businesses are now using VoWLAN. The researchers expect that percentage to reach 31 per cent by 2007.

The main reasons now holding back the uptake of wireless LANs in business are fears over security and privacy.

Wireless VOIP Growth

Wi-

Fi P

DA

s &

Lap

top

sMobile Users802.11 Footprint

More Wi-Fi DevicesMore Places to Use

More Mobile Users

Conclusion Technology exists today to implement VoIP over

WLANs applications as an integral part of next-generation seamless wireless voice/data networks.

The wireless industry has already begun to migrate toward an environment where one phone number can be used practically anywhere for voice and data applications.

To accomplish this goal, mobile device designers, carriers, service providers and enterprise/home network designers face deployment, provisioning and implementation issues.

References http://www.wi-fiplanet.com/news/article.php/

1015241 http://www.cisco.com/en/US/products/hw/phones/

ps379/products_administration_guide_chapter09186a008024662c.html

http://www.technologyreview.com/articles/04/08/wo_brown081104.asp

http://www.wired.com/wired/archive/11.06/start.html?pg=8

http://www.wi-fitechnology.com/wi-fi_forum_submit_news.shtml

http://www.crm2day.com/experts/EEpAZyuAuVgLprsEUp.php

Source: http://news.zdnet.com/2100-1035_22-5571870.html

http://www.wi-fitechnology.com/user.php http://www.telecomasia.net/telecomasia/article/

articleDetail.jsp?id=168107 http://www.commweb.com/showArticle.jhtml?

articleId=168601894 http://www.google.com/search?

hl=en&q=find+voice+over+wifi www.intel.com www.doceotech.com

QUESTIONS 1.What are the technical issues and challenges

involved in VoWiFi? Write about the quality of service in VoWiFi?

2.Advantages and Disadvantages of VoWiFi? 3.What are the Common Vo WiFi Infrastructure

Problems?

SOLUTIONS 1. The Technical issues of VoWiFi are

Quality of Service (QoS)Proper bandwidth Security and privacy Interoperability Interference and complexity

The Technical challenges are Deliver High Quality without QoSDeal with High Packet Loss on WLANsRoaming Across WLAN Network SegmentsRoaming From WLAN to CellularCompatibility with Firewalls

2. The Advantages of VoWiFi- Mobility is the primary selling point, much as it is with cell

phones. VoWiFi has the advantage of no airtime charges. As a

wireless technology, there are no wires to run to Wi-Fi phones. Therefore, network configuration and reconfiguration processes are fast.

VoWiFi delivers a simpler, less expensive and more flexible system for providing mobile data and voice communications than other technologies that require the implementation and maintenance of separate systems for each.

VoWiFi also offers greater reliability and voice quality than alternatives such as cellular technology

Disadvantages of VoWiFi- VoIP and Wi-Fi are both immature technologies, so merging the two

into VoWiFi carries some associated risks. Standards are still in development, and some early pre-standard

versions may not be upgradeable to compliance level. As a data-centric LAN technology, Wi-Fi involves a shared medium

in the form of frequency bands creating issues of contention and congestion

Troublesome for stream-oriented communications such as voice, and especially so when handoffs are required as the user roams between APs.

Costs have to be considered, of course, and the cost of a VoWiFi LAN can be double that of a data-only WLAN.

Wi-Fi phones are easily double the cost of a typical cordless phone.

Current Wi-Fi phones don’t have much, although the next generation or two should overcome that issue.

3. Scalability Quality of Service Usability

• QuestionsQuestions ？？• CommentsComments ？？• SuggestionsSuggestions ？？